[vis,agg_types] standardize dsl uses as 'toDsl' or 'dsl'

src/kibana/apps/discover/controllers/discover.js

@@ -632,7 +632,7 @@ define(function (require) {
       });
 
       $scope.searchSource.aggs(function () {
-        return $scope.vis.aggs.toDSL();
+        return $scope.vis.aggs.toDsl();
       });
 
       // stash this promise so that other calls to setupVisualization will have to wait

src/kibana/apps/visualize/saved_visualizations/_saved_vis.js

@@ -89,7 +89,7 @@ define(function (require) {
         }
 
         self.searchSource.aggs(function () {
-          return self.vis.aggs.toDSL();
+          return self.vis.aggs.toDsl();
         });
 
         return self;

src/kibana/components/agg_types/_agg_params.js

@@ -57,7 +57,7 @@ define(function (require) {
      *         the quality of things like date_histogram's "auto" interval)
      * @return {object} output
      *         output of the write calls, reduced into a single object. A `params: {}` property is exposed on the
-     *         output object which is used to create the agg DSL for the search request. All other properties
+     *         output object which is used to create the agg dsl for the search request. All other properties
      *         are dependent on the AggParam#write methods which should be studied for each AggType.
      */
     AggParams.prototype.write = function (aggConfig, locals) {

test/unit/specs/components/agg_types/bucket_aggs/date_histogram.js

@@ -30,7 +30,7 @@ define(function (require) {
       }));
 
       describe('interval', function () {
-        // reads aggConfig.params.interval, writes to DSL.interval
+        // reads aggConfig.params.interval, writes to dsl.interval
 
         it('accepts a number', function () {
           var output = paramWriter.write({ interval: 100 });

test/unit/specs/components/agg_types/bucket_aggs/histogram.js

@@ -30,7 +30,7 @@ define(function (require) {
       }));
 
       describe('interval', function () {
-        // reads aggConfig.params.interval, writes to DSL.interval
+        // reads aggConfig.params.interval, writes to dsl.interval
 
         it('accepts a number', function () {
           var output = paramWriter.write({ interval: 100 });